The present invention relates generally to security alarm systems and more particularly to a door lock assembly, particularly a mortise lock, including an electrical alarm system. More specifically, the invention involves a lock assembly which includes a lock frame and a lock bolt which may be moved out of the lock frame into locking position. An electrical alarm system is actuated by an alarm element formed as part of the lock assembly which energizes the alarm system to produce a signal when pressure is applied upon the lock bolt of the assembly.
A door lock assembly of the type to which the present invention relates is known from German Auslegeschrift 20 30 867 wherein an alarm element is constructed as a switch contact which transmits an electrical voltage and which is connected to the input of an alarm system spatially separated from the door itself. The switch contact is actuated by a guide sleeve of the lock bolt of the system which is pivoted transversely relative to the door together with the lock bolt when a tractive or compressive force is applied to the door. However, due to the relatively long distance through which the switch contact must move in order to release the alarm, the lock bolt of this known door lock alarm system must be guided in the lock frame with a relatively large degree of play. This results in that the door cannot be closed with a snug fit. Moreover, the pivotal support of the lock bolt in the lock frame requires additional measures and it is therefore not possible to equip door locks of any selected type with the alarm element.
The present invention is directed toward providing a system wherein door locks may be equipped with an alarm element without requiring changes in the design of the lock bolt guide, with the alarm element of the invention responding to the opening of the door when the lock bolt is moved out of the locking position.